Collision preventer



P 1962 J. K. FIGENSHAU ETAL 3,053,948

COLLISION PREVENTER 2 Sheets-Sheet 1 Filed June 9, 1960 INVENTORS JAMES K. FIGENSHAU WILLIAM H. HAINER AGENT Sept. 11,1962 J. K. FIGENSHAU ETAL COLLISION PREVENTER 2 Sheets-Sheet 2 Filed June 9, 1960 IIIII INVENTORS JAMES K. FIGENSHAU WILLIAM H. HAINER Patented Sept. 11, 1962 3,053,948 COLLISION PREVENTER James K. Figenshau, Big Lake, and William H. Hainer, St. Paul, Minn, assiguors to General Mills, Inc, a corporation of Delaware Filed .l'nne 9, 1960, Ser. No. 35,026 11 tijlaims. (Cl. Mill-451.42)

This invention relates to collision preventers and more particularly to collision preventers for protecting movable devices from cOlliSiOns regardless of the direction from which the device approaches the obstruction.

A variety of devices have been proposed for limiting the motion of moving elements with respect to other objects. Among such devices are the limit switches used in elevators, cranes and the like for preventing the elevator car from striking either the top or bottom of the elevator shaft. Another class of devices includes strategically located signaling probes which project outwardly from vehicles such as lift trucks or automobiles and are used to detect the approach of an obstruction such as acurbstone.

'In contrast, with the prior art, the present invention is directed toward providing a means for detecting collision between obstructions and a device for which protection is desired even though the direction from which the device approaches the obstruction cannot be exactly anticiplated. A further provision of the present invention includes means for automatically stopping the motions of the device protected before a collision occurs. The present invention is particularly valuable for applications in protecting bodies movable in several directions with respect to a base, such as the moving arm or mast portion of hoists, cranes, mechanical arms and the like.

In recent years remote handling epuipment has become an important phase of the atomic industry among Others. Included in such remote handling devices are crane hoists, underwater corrosion resistant manipulators, manned and unmanned mobile manipulators, fuel handling devices and mechanical arms. The mechanical arm is a remote controlled device which will duplicate one or more motions of the human arm and hand with extreme accuracy. Because of the precision tolerances maintained in these devices, it is highly desirable to protect them from potentially damaging collisions. The term arm as used herein is defined as any elongate rember attached movably to a frame or base and is meant to include masts, booms and the like. It will be appreciated that as a result of the large number of possible motions of the several parts of the arm, occasionally when operated by remote control the arm may strike an obstruction unnoticed by the operator. Furthermore, it is impossible to anticipate which part of the arm will contact the obstruction. Therefore,- to protect the arm from collisions, it is desirable to provide means for detecting and preventing contact with obstructions on all sides of the arm. The protector must be reliable in operation, light in weight, positive in action and should remain undamaged after engagement with an obstruction.

It is an important object of this invention to provide an improved collision sensing envelope for a material handling device, which is external to and extends almost completely around the device to be protected.

It is another object of this invention to provide an improved collision preventer which readily senses an impending collision and promptly stops the motion of the device to be protected before damaging contact occurs.

It is a further object of this invention to provide an improved collision preventer of a mechanical type which is very reliable and wherein collisions are non-damaging both to the protection device and to the device protected.

It is still another object of this invention to provide an improved collision detecting and preventing device which will protect the device effectively from collisions with foreign objects at any side of the device to be protected.

These and other objects will be apparent from the accompanying description.

Briefly stated, the present invention includes a device for mechanically detecting and preventing an impending collision between a physical obstruction and a device to be protected such as an arm or mast movable with respect to a base or other support. It preferably includes means for interrupting the arm drive motion before the arm itself contacts the obstruction.

According to one embodiment of the present invention there is provided a detector means such as a series of detector wires or cables extending parallel to the longitudinal axis of the moving device or arm for which protection is desired and arranged so as to provide a protective detector envelope or cage spaced from the device. The wires are secured at each end to ring like support members which are in turn flexibly and resiliently mounted near the ends of the device to be protected. In the preferred embodiment of the invention, one of the support members is designed to operate sensor means such as electrical switches whenever the detector means and support means is deflected by engagement with an obstruction. The switch can thus stop any or all drive motions for the device before the device itself contacts the obstruction. The resiliently mounted detector rings may also be provided with sensing means such as rods or the like which extend the collision detecting envelope beyond the ends of the arm. A provision is also made so that when either of the Support means is struck, it will tilt, and as a result of the linkage through the detector envelope, the other spring mounted ring will be caused to tilt so that the sensor means are always actuated no matter where contact takes place between the envelope and the obstruction.

This invention will be best understood from the illus-. trations in the accompanying drawings showing one form of apparatus according to the present invention is which:

FIG. 1 is a side elevation of a mechanical arm utilizing one form of apparatus embodying the present invention.

FIG. 2 represents a perspective view partly in section illustrating another form of apparatus in which the collision preventer according to this invention may be utilized.

FIG. 3 is a side elevation of one form of apparatus in accordance with this invention which may be used with either of the devices illustrated in FIGS. 1 and 2.

FIG. 4 is a plan view taken along line 4-4 of FIG. 3.

FIG. 5 is a side elevation partly in section of a support plate mounting spring.

With reference to these figures, there is shown in FIGURE 1 a mechanical arm 1 having a cylindrical upper arm member 2 fixed rigidly to a suitable shoulder or overhead supporting framework 4. Mounted atthe lower end of upper arm portion for rotation about the longitudinal axis of the upper arm member is a pivot support member 7. Rotation of the pivot support member 7 is carried out by electric motors inside the upper arm 2 and is controlled by means of a remotely placed motor control. Secured rigidly to the pivot support member 7 is a lower arm pivot bearing 3. Pivotally mounted on the lower arm pivot bearing 3 for motion about an axis transverse to the arm is a lower arm member 16 having a pair of jaws 5 extending therefrom. The jaws 5 are rotatably mounted with respect to the lower arm 16 and may be rotated as well as opened and closed by a remotely controlled motor recessed inside the arm. The collision preventer mechanism designated 6 is suspended from the lower arm 16 and will be described in detail below.

Referring now to FIGURE 2, there is shown another device embodying the present invention which is generally similar to an overhead crane comprising a bridge 11 supported at either end by wheels .12 resting. on tracks 13 and 14 and a carriage 15 having wheels mounted on the bottom thereof for carrying the carriage 15 across beam 11. Inside the carriage 15 is provided an electric motor (not shown) for moving the carriage 9 with respect to the beam 11. Extending vertically downward and upward from the carriage is a cylindrical arm or mast 16a which may be elevated or lowered by any suitable means known to the art such as by an electric motor geared to a rack extending the length of the arm. At the bottom of the arm may be provided any desired variety of sensing or lifting mechanism 17 such as a pair of jaws or the like. For purposes of illustration, an ionizing radiation sensing probe is shown. Conductors for carrying the current to the sensing mechanism may be recessed inside the arm 160. By means of such a device, measurements may be taken or articles may be picked up and moved about and positioned with accuracy.

The collision detecting mechanism used in the devices illustrated in FIGURES l and 2 will now be described in detail in which the same numbers refer to corresponding parts. With particular reference to FIGURES 3 and 4, there is shown at the top and bottom of arm 16 a pair of flat support members or rings 20 and 21 respectively. Each of rings 20 and 21 has a hole in the center thereof designated 22 and 23 respectively. Arm 16 passes through the center of holes 22 and 23. The holes are preferably substantially larger in diameter than the diameter of the arm. For example, they may be on the order of one and one half times the diameter of the arm. The size of the holes is not critical but is preferably larger in cases in which the arm is designed to operate at relatively high speeds or when movement of the mast cannot be stopped rapidly as explained more fully hereinbelow. The shape of the detector ring in plan view is illustrated as octagonal, however the shape is not critical and it could be round or square if desired.

Ring 20 is flexibly and resiliently suspended from arm 16 by eight helical springs 25 each connected at one end to the arm 16 above ring 20 and at the other end to the detector ring 20. Ring 21 is suspended in a similar manner by eight helical springs 26 each being attached to the ring 21 at one end and to the arm 16 below the ring at the other end. Extending between ring 20 and 21 substantially parallel with the arm 16 is a detector means comprising a plurality of detector cables 19. The detector cables 19 are spaced apart and attached at each end to the outside edges of the rings 20 and 21 thereby surrounding the arm throughout almost its entire length so as to form a cage or envelope around the arm. Rigidly attached to the periphery of detector ring 21 and extending downwardly therefrom are a plurality of spaced-apart sensing rods 24, four such rods being shown.

As shown in detail in FIG. 5, each of springs 25 and 26 is fitted at either end with a spring retainer 27 and a threaded eyebolt 2S screwed into the center of the retainer 27. The eyebolts extending upwardly from the springs designated 25 are connected to spring brackets 29 which are attached rigidly to the arm. The eyebolts extending downwardly from spring 25 are connected to suitable brackets 30 attached securely to detector ring 20. Similarily, the eyebolts 28 attached to springs 26 at their lower ends are connected to brackets attached rigidly to the arm and those attached to the upper end of the springs are connected to brackets 36 mounted on detector ring 21. The four brackets designated 29 attached to the arm are spaced axially apart from, and positioned circumferentially between the four brackets 30 attached to the arm. Each bracket 29 thus has two springs 25 attached thereto and each such pair of springs diverges so that the lower ends thereof are attached to brackets 30 on either side of the racket 29 to which the upper end thereof is attached.

Springs 26 are mounted in a manner similar to that hereinbeforc explained in connection with spring 25. The brackets mounted on the detector rings 20 and 21 are also positioned farther from the axis of the arm than those on the arm. Thus, it will be noted that the springs are inclined at an acute angle with respect to the axis of the mast, and the ends thereof connected to rings 20 and 21 are spaced further apart than the ends connected to the arm. The springs 25 and 26 thus simultaneously suspend the detector envelope movably, center the detector envelope with respect to the arm axis, and maintain tension on the cables so that any cable movement results in a corresponding ring movement.

Attached rigidly to arm 16 above deflector ring 20 and spaced therefrom is a switch support member 40. Support member 40 may be mounted at any convenient position on the arm and the length of cable 19 adjusted to maintain ring 20 at the desired distance from support member 40. Mounted at equally spaced apart intervals on the periphery of the support member 40 are four pairs of electrical switches 42, and 42a, 43 and 43a, 44 and 44a, 45 and 45a. Conductors 46 wired to the switches are connected in series with the drive motor (not shown) which is used for moving the arm. These switches are preferably maintained in a normally closed position so that the circuit carrying current to the drive motor is complete. If, however, the switches are opened, current to the drive motor will be interrupted and the motion of the arm is thereby stopped. Each switch has a button 50 on the lower side thereof which, when moved slightly will turn the switch on or off. The position of the ring 20 is so adjusted that the upper surface thereof contacts all of the several switch buttons and maintains the switches in the closed position.

Switches 42, 43, 44 and 45 are opened when their respective buttons 50 are released and switches 42a, 43a, 44a and 450 are opened when their respective buttons 50 are depressed. As a result, one switch of each pair will be opened whether the portion of ring 20 adjacent a given pair of switches is depressed or elevated thereby assuring reliable performance. -It will be seen that when any of the cables or rings are deflected by an obstruction or in any way caused to move relative to mast 16, plate 20 will also move so that at least one switch button will be depressed or released thereby opening the circuit to the drive motor. For example, if a foreign ob ject or obstruction strikes one or more of the cables on the right side of the apparatus in FIG. 3, the lower ring will tilt counterclockwise and the upper ring will tend to tilt clockwise activating switches 42 and 4411. If the cables are struck from the front in FIG. 3, switches 43 and 45a will be activated. It will be noted that if either of the rings itself is hit from the side and moved laterally, a tilting action will still take place because of the fact that the ends of the springs mounted to the arm (since they are closer together than the ends mounted on the rings) form a pivot point about which the rings turn even though displaced laterally. Thus when ring 21 is struck from the right side in FIG. 3 and displaced laterally to the left, it will rise on the right side and descend on the left side, thereby tilting plate 20 by virtue of a connection through cables 19 in a counterclockwise direction (as seen in FIG. 3). This tilting causes the buttons of switches 44 and 44a to be depressed and the buttons of switches 42 and 42a to be released.

In determining how far the protective envelope should be spaced from the device to be protected, one must consider the distance in which the device can be decelerated and stopped. If this distance is fairly great, the envelope and holes in rings 20 and 21 should be spaced further from the arm 16 so that the device can be stopped before collision takes place between the obstruction and the arm or between the rings and the arm.

A number of variations are possible in the present invention. The electric switches, for example, can be replaced by pneumatic or hydraulic valves if desired. This change would be preferred if the drive mechanism were operated by pneumatic or hydraulic actuators. Electric switches, of course, are preferred when the drive motor or mechanism is electrically operated. The switches themselves may be either normally open switches or normally closed switches. The switches may be mounted on either the device to be protected, that is the mast or arm in the present illustration or on the cage or envelope or a portion thereof or on the detector ring.

The suspension means have been illustrated as springs, but it is apparent that other resilient and extensible or flexible devices may be used to accomplish the same result. For example, sponge rubber mounts may be used or a form of rubber tubing may be used, if desired. A form of gimbal mechanism may be substituted for the springs but it should be noted that the gi-mbal mechanism must be designed so as to enable the protective envelope to be moved in all directions including vertically and must also be provided with a'centering means.

The detector means or envelope has been illustrated as a plurality of parallel cables extending from a ring at the lower end of the mast to a ring at the upper end of the mast, but a number of other variations are possible. 'For example, a flexible screen or mesh could be substituted for the cables and if the obstructions likely to be encountered are pointed projections having a small area at the end, a tube of material such as cloth or plastic film could be used which would have the advantage of forming a continuous envelope around the device to be protected. Thus, no matter how small the obstruction was, it could not collide with the device without first striking the detector.

In view of the principles set forth herein, we have shown some of the ways of carrying out the present invention and some of the equivalents which are suggested by these disclosures.

We claim:

1. A collision preventer comprising an arm to be protected, first and second movable support means encircling said arm and spaced therefrom, resilient suspension means for said support means connected between said support means and said arm normally holding said support means in one position on said arm whereby said support means may be displaced with respect to said arm, a plurality of detector means extending from said first sup port means to said second support means and a sensor means operatively associated with said arm and said support means for detecting relative displacement between either of said support means and said arm.

2. A collision preventer according to claim 1 wherein said resilient suspension means comprises a plurality of spaced apart springs disposed about the circumference of each said support, each such spring being connected at one end to one said support and at the other end to said arm.

3. A collision preventer according to claim 1 wherein said sensor means comprises means for making and breaking an electric circuit operatively connected between said support means and said arm whereby displacement of said support with respect to said arm activates said circuit making and breaking means.

4. A collision preventer according to claim 3 wherein said circuit making and breaking means comprises a plurality of electric switches wired in series with the drive mechanism for said arm.

5. A collision preventer comprising an elongate body to be protected, a first movable support member encircling one end of said elongate body and spaced therefrom, a second movable support member encircling the other end of said elongate body and spaced therefrom, a plurality of spaced apart resilient suspension members disposed about the circumference of each said support and connected at one end to one said support and at the other end to said elongate body whereby said supports are movably mounted and normally held in one position with respect to said elongate body, detector means extending from one said support to the other said support, and electric switch mean operatively associated with said body and said first support member whereby displacement of said first support with respect to said elongate body activates said switch means.

6. A collision detector comprising a movable arm to be protected, a first support member encircling one end of said arm and spaced therefrom, a second support member encircling the other end of said arm and spaced therefrom, a plurality of spaced apart springs disposed about the circumference of each said support, said springs being connected at one end to said support and at the other end to said arm, the axis of each such spring intersecting the axis of said arm at an acute angle, the ends of said springs connected to said support being spaced relatively far apart and the ends of said springs connected to said arm being spaced relatively close together, and a plurality of electric switches operatively associated with said support and wired in the circuit controlling the driving mechanism for said arm whereby displacement of said support with respect to said arm causes said arm to stop moving.

7. A collision preventer comprising an arm to be protected, a movable support ring encircling one end of said arm and spaced therefrom, resilient suspension means for said ring connected between said ring and said arm whereby said ring is movably mounted and normally held in one position with respect to said arm, flexible detector means surrounding said arm and connected between said ring and the other end of said arm and sensor means connected to said arm to halt the motion of said arm responsive to displacement of said ring with respect t said arm.

8. A collision preventing mechanism comprising a framework; an elongate arm connected to said framework, said arm being movable with respect to said framework; a drive mechanism for moving said arm; switch means for starting and stopping said drive mechanism; detector means extending along the length of said arm and surrounding said arm for transmitting relative motion between foreign objects and said arm to said switch means, said switch means being activated when a foreign object strikes said detector means, said detector means including an axially extending detector element and a movable support member connected to and supporting one end of said detector element, and suspension means connected at one end to said arm and at the other end to said support means for mounting said support means movably and normally in one position with respect to said arm.

9. A collision preventer according to claim 1 wherein said arm has connected at the free end thereof a gripping device and wherein one said support means has connected thereto a plurality of elongate sensing members disposed laterally from said gripping device.

'10. A collision preventer comprising an arm to be protected, first and second support means encircling aid arm and spaced therefrom, resilient suspension means for said support means connected between said support means and said arm normally holding said support means in one position on said arm whereby said support means may be displaced with respect to said arm, said resilient suspension means comprising a plurality of spaced apart springs disposed about the circumference of each said support, each such spring being connected at one end to one said support and at the other end to said arm, each such spring intersecting the axis of said arm at an acute angle, the ends of said springs connected to said support being spaced relatively farther apart than the ends of said springs connected to said arm, a plurality of detector means extending from said first support means to said second support means and a sensor means for detecting relative displacement between either of said support means and said arm.

11. A collision preventer comprising an arm to be protected, first and second support means encircling said arm and spaced therefrom, resilient suspension means for said support means connected between said support means and said arm normally holding said support means in one position on said arm where-by said support means may be displaced with respect to said arm, a plurality of detector means extending from said first support means to said second support means and a sensor means for detecting relative displacement between either of said support means and said arm, said sensor means comprising means for making and breaking an electric circuit and means operatively associated therewith whereby displacement of said support with respect to said arm activates said circuit making and breaking means, said circuit making and breaking means comprising a plurality of electric switches wired in series with a drive mechanism for said arm, said electric switches comprising four pair of equally spaced apart switches, one switch of each pair being opened when the switch element thereof is depressed and the other switch of each pair being opened when the switch element thereof is elevated.

References Cited in the file of this patent UNITED STATES PATENTS 

